ABSTRACT
Candida is a commensal fungus found in the gastrointestinal tract (GI), genitourinary tract, mouth, and skin. In healthy individuals, it does no harm. However, in immunocompromised people Candida can cause a range of pathologic conditions from mild superficial infections to life-threatening invasive candidiasis (IC) which comprises candidemia (bloodstream infection), disseminated, and deep-seated candidiasis. Currently, C. albicans is a leading cause of hospital-acquired infections with 47% mortality in intensive care unit (ICU) patients.
C. albicans appears in two reversible morphologic forms: unicellular budding yeast and filamentous form (hyphae and pseudohyphae). Yeast cells have a round-to-oval morphology, while hyphae consist of firmly attached branched tubular cells. The hyphal form is required at the early stage of infection, penetrating the tissues, while the yeast form is needed for adhesion to endothelial cells and dissemination into the bloodstream.
Innate immunity is essential at preventing opportunistic invasion of C. albicans. The phagocytosis of C. albicans by macrophages and polymorphonuclear neutrophils (PMNs) is critical for the effective clearance of C. albicans from the host tissue. During immune suppression, C. albicans can overcome the innate immune system and switch from a harmless commensal to a pathogenic growth. The adaptive immune response against fungal commensals in the normal skin and gut is mainly generated through T-helper (Th)17 and Th1 cells.
The main forms of candidiasis are candidiasis of the mouth and throat (oropharyngeal candidiasis or thrush) and esophageal, vaginal or vulvovaginal candidiasis and the most severe form – invasive candidiasis (IC), often associated with high rates of morbidity and mortality and increased lengths of hospital stay. IC is diagnosed by fungal culture (golden standard), serology and polymerase chain reaction (PCR). Three classes of antifungal drugs are used as first-line treatment of IC: polyenes (amphotericin B), azoles (fluconazole) and echinocandins (anidulafungin, caspofungin, and micafungin). There is currently no vaccine for Candida.
